| Satellite precipitation estimation is a significant advance in the field of atmospheric precipitation observation,but the performance of satellite products is closely related to the terrain,geographical location and climate characteristics of the study area.The Nanliujiang River Basin in Guangxi is a coupled region of tropical,coastal and karst-hilly combines landforms.In this paper,IMERG,the GPM Level-3 product,is selected as the research object.The hourly data of 14 ground stations in the Nanliujiang River Basin are taken as the reference.The rainfall detection ability,correlation and error of daily,hourly and monthly rainfall estimates with ground precipitation are evaluated respectively.Then,the relationship between error and the average rainfall of the ground and satellite in the selected time period and the geographical conditions of the basin are analyzed.The effect evaluation of the post-real-time satellite precipitation product self-correcting process is discussed.Finally,by introducing the parameter CPI(Comprehensive Performance Index)to quantify the comprehensive performance of satellite,the comprehensive performance of each product at each gauge station under different product verification combinations is evaluated.The main conclusions are as follows(1)IMERG rainfall estimates have the strongest ability to detect weak precipitation in the Nanliujiang River Basin,and its ability to detect precipitation decreases with the increase of rainfall threshold.This is mainly due to the expansion of the measurement range of the latest sensors carried by GPM and the enhancement to detect weak precipitation and snowfall.With the increase of spatiotemporal scale,the correlation between rainfall estimation and ground data increases,and the change of spatiotemporal scale is related to error smoothing.(2)There are some reasons for the deviation of satellite precipitation estimates in the Nanliujiang river basin: Firstly,the number of ground rainfall stations cannot meet the requirements of IMERG product evaluation.Secondly,the accuracy of the measuring equipment itself leads to the deviation of the original ground observation data.Thirdly,there is no GPCC station for self-calibration of IMERG data in the Nanliujiang River Basin.Furthermore,the spatial sensitivity of smooth and balanced satellite precipitation estimation is not enough,Lastly,the sensitivity of satellite estimates to seasonal variations is limited.(3)The geographical location of the Nanliujiang River Basin will affect the performance of IMERG rainfall estimation.Because the GPROF database used in IMERG products underestimates precipitation in coastal areas,the poor performance of the database in coastal areas has led to that IMERG satellite rainfall data underestimate ground precipitation in coastal areas such as the Nanliujiang River basin.(4)Among the 14 stations of the Nanliujiang River Basin,the CPI of IMERG is higher than that of TMPA in 11 stations,which indicates that the comprehensive performance of IMERG has obvious advantages compared with the previous generation product.The advantages of IMERG in comprehensive performance are very limited due to the version upgrade,and the CPI of the latest version V06 is higher than that of V05 in only 8 stations.Among the three IMERG products,IMERG-F has the strongest comprehensive performance. |
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